1. Field of the Invention
This invention relates to the cutting of materials by high temperature oxidation, and it more particularly relates to systems for underwater oxygen-arc cutting of work pieces.
2. Description of the Prior Art
The technique of arc-oxygen underwater cutting of work pieces (metal, concrete, etc.) has been practiced for many decades. In this operation, a DC or AC current is passed between a cutting rod and the work piece as the other terminal of the system to establish an arc. Simultaneously with the arc, a flow of oxygen down the rod causes oxidation at very high temperatures which readily cuts steel, other metals, rock, concrete and other materials. The rod not only serves to apply the arc and oxygen to the work piece, but also can be used as a gouging, prying and picking tool by the diver performing the underwater cutting work.
The rod has been a ferrous metal tube filled with metallic wires surrounding an oxygen flow path, and these wires can be iron and other ferrous alloys, copper, aluminum, magnesium and various mixtures of these metals. The rods were supposedly designed for certain underwater cutting purposes as to size, length and metal compositions.
Usually, the rod was of a construction to be used at 300-400 ampere current flows with an oxygen pressure (at the rod) of about 100 PSI above water pressure at the depth of the work piece. The current magnitudes and oxygen pressures have been varied by whim, prejudice or preference of the diver to complete the underwater cutting work in the best and quickest manner.
Various rods have been used and range from a simple 5/16 inch OD steel tube, 14 inches long with an axial bore of about 1/8 inch to composite rods alleged to have a thermite effect. The latter rods include a "Thermal Lance" which was a 3/8 inch pipe, 10 feet, 6 inches long that was packed with a number of different metal alloys, such as aluminum, magnesium, thermite and steel. When the Thermal Lance rod was ignited and oxygen flow established through it, the rod burned with tremendous heat which was claimed to reach a temperature of 10,000 degrees for about six minutes. The rods can be extinguished only by shut-off of the oxygen flow. The Thermal Lance rod was marketed under the name "Burning Bar".
Reference for these rods may be taken to the literature references "Marine Salvage Operations", Cornell Maritime Press, Inc., 1960 at pages 207-208 and "Commercial Oil-Field Diving", Cornell Maritime Press, Inc., 1971, at pages 151-169.
The following patents also describe various cutting rods some of which may be used in underwater oxy-arc cutting work:
______________________________________ 2,802,390 B. M. Ronay Issued 8/13/75 (Class 219) Showing a cast iron alloy tubular rod; 3,260,076 W. Humberg Issued 7/12/66 (Class 431) Showing a steel burner pipe filled with steel and magnesium wires; 3,507,230 H. A. Sieb Issued 4/21/70 (Class 431) Showing a composite rod of a steel tube filled with low carbon steel and aluminum rods; 3,507,231 R. Meir Issued 4/21/70 (Class 431) Showing a composite rod similar to Seib but with an annular groove/ring to secure the wires to the burner pipe; 3,591,758 R. Clucas Issued 7/6/71 (Class 219) Showing a flexible composite rods having a plastic sheath filled with steel wires surrounding the oxygen passageway; 4,069,407 J. S. Bower Issued 1/17/78 (Class 219) Showing a composite rod identical to Seib or Meir but having a mixture of steel and aluminum or titanium, or alloys thereof for a "thermite effect" burning rod which can be extinguished after ignition only by shut-off of the oxygen flow; and 4,182,947 J. S. Bower Issued 6/8/80 (Class 219) 4,416,444 J. S. Bower Issued 11/22/83 (Class 219) Shown with composite rod like 4,069,407 but with non-ferrous coated steel tubing to produce "thermite effect" in a burning rod even with current supply interrupted. ______________________________________
In summary, the past use of cutting rods in underwater oxy-arc work left the design of the rods and other cutting parameters (sizes, current, gas flow) much to chance as long as the rods did the work. For example, many rods were designed to continue burning (thermite effect) once ignited even though the arc was quenched by interrupting current flow. Only oxygen shut-off stopped the continued high rate consumption of these rods. Since the object of underwater cutting is to burn-cut the work piece and not the rod, these rods were inefficient, especially the "Thermite Effect" type of rods.
The tubular cutting rod life should be spent in cutting the work piece since the divers time is limited, very expensive because of his great specialized skills, and the pressing need to complete the underwater cutting work. Also, frequent replacements of self consuming cutting rods is not a desired hobby of the diver.
In the same regard, the cutting rod and cutting system should be optimized for the fastest cutting with the least diver time, oxygen and current consumed, and with the best cutting rod life.
The present improved system for underwater oxy-arc cutting of a work piece, and the unique rod used in such work, are directed to the above-recited optimization.